Earth's Core Is Getting Bigger

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The Earth's inner core is mostly made of iron, though whether it's a pure solid is up for debate. Temperatures at the planet's center far exceed the melting point of iron, but high pressure keeps the core from transforming into a liquid. (Some scientists classify it as a plasma that acts like a solid.) Every year, the inner core grows by about a millimeter as parts of the outer core solidify. The process is uneven, and unlikely to ever completely "freeze" the outer core, which would take around 91 billion years. Learn more about Earth, and our neighboring planets, below.

Everything You Need to Know About Planet Earth

But, there's still so much more we need to understand.

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Key Facts In This Video

  1. 97.5% of the water on Earth is saltwater, and only 2.5% is fresh water. 01:52

  2. Earth's outer core is a liquid layer of iron and nickel. 03:53

  3. Humans have only been around for about 0.004% of Earth's history. 06:29

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What You Need To Know About Our Neighboring Planets

Neptune has a mass the equivalent of 17 Earths.

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Key Facts In This Video

  1. Planets, asteroids, and other matter make up only .14% of the solar system's mass. 00:06

  2. Pluto won't complete its next full orbit around the sun until the year 2177. 01:01

  3. Jupiter might contain water droplets in certain gas layers. 02:45

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